Used commercially in the 1860s, it was the first device to enter practical service and could send handwriting, signatures, and drawings up to 15 cm by 10 cm.

Using a regulating clock and a pendulum to ensure that it could make and break the current for magnetizing its regulators, as well as ensuring the transmitter’s scanning stylus and the receiver’s writing stylus stayed synchronized.

The receiver reproduced the image by using paper with potassium ferricyanide, which darkened when an electric current passes through it.